Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$202.88	8.782%	$220.6969	$220.70	$220.70	$220.70
Purchase #2	$29.95	6.446%	$31.8806	$31.88	$31.90	$31.90
Purchase #3	$109.81	7.854%	$118.4345	$118.43	$118.45	$118.40
Purchase #4	$182.59	7.714%	$196.675	$196.68	$196.70	$196.70
Purchase #5	$86.86	5.436%	$91.5817	$91.58	$91.60	$91.60
Purchase #6	$57.95	3.211%	$59.8108	$59.81	$59.80	$59.80
Purchase #7	$127.60	8.468%	$138.4052	$138.41	$138.40	$138.40
7 purchase totals =	$797.64		$857.4847	$857.49	$857.55	$857.50